1. Field of the Invention
The present invention relates to a camera module and a method of manufacturing the same.
2. Description of the Related Art
Recently, camera modules are mounted on IT devices such as mobile terminals, PDAs (Personal Digital Assistant), MP3 players and so on. With the development of technology, the resolution of the camera modules changes from 300,000 pixels (VGA) to several million pixels, and the reduction in size and thickness of the camera modules are being performed depending on mounting targets. Further, the camera module provides various additional functions, such as auto-focusing (AF) and optical zoom.
The camera modules are manufactured by using main parts of charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS) image sensors. Incident light transmitted through the lens is condensed by the image sensor and is stored as data in a memory. The stored data is displayed as an image through a display medium, such as liquid crystal display (LCD) or PC monitor.
Typical camera modules are manufactured by a chip-on-film (COF) method, a chip-on-board (COB) method and the like. The COB method will be described with reference to drawings.
FIG. 1 is an exploded perspective view of a conventional camera module manufactured by the COB method, and FIG. 2 is a cross-sectional view of the conventional camera module.
In the conventional camera module 10, a printed board 11 having a CCD or CMOS image sensor 12 mounted thereon through wire bonding is coupled to a lower end portion of a housing 13 formed of plastic, and a lens barrel 16 having a cylindrical body 14a extending downward is coupled to a lower end portion of a barrel 13a extending upward from the housing 13.
In the camera module 10, the housing 13 and the lens barrel 14 are coupled to each other by coupling a female screw portion 13b formed on the inner circumferential surface of the barrel 13a to a male screw portion 14b formed on the outer circumferential surface of the cylindrical body 14a. 
Further, an IR filter 15 is interposed between a lens 14c mounted in the lens barrel 14 and the image sensor 12 attached on the upper surface of the printed board 11 so as to cut off excessive long-wavelength infrared rays incident on the image sensor 12.
In the camera module assembled in such a manner, while light incident from a specific object passes through the lens 14c, an image is inverted so that the focus is adjusted on the surface of the image sensor 12. At this time, when a focus is optimally adjusted while the lens barrel 14 screwed to the upper end of the housing 13 is rotated, an adhesive is injected between the barrel 13a of the housing 13 and the lens barrel 14 such that the housing 13 and the lens barrel 14 are bonded to each other. Then, the camera module is finalized.
In the camera module manufactured by the COB method, the lens barrel 14 is inserted into the upper opening of the housing 13 such that the lens barrel 14 and the housing 13 are closely coupled to each other through the screw coupling using the female and male screw portions 13b and 14b formed on the inner and outer circumferential surfaces of the housing 13 and the lens barrel 14. As height adjustment is performed by rotating the lens barrel 14 at the upper end portion of the housing 13, focus adjustment between the lens 14c within the lens barrel 14 and the image sensor 12 mounted on the printed board 11 is achieved.
Therefore, in the conventional camera modules manufactured by the above-described assembling method, when the housing 13 and the lens barrel 14 are vertically coupled, and if the female and male screws 13b and 14b are engaged at a distorted angle, screw threads may be broken or the coupling portion may be worn away by the friction between the female and male screws 13b and 14b. Then, foreign matters such as minute particles may occur, thereby degrading the assembling property.
Further, the particles occurring between the housing 13 and the lens barrel 14 inevitably fall onto the upper surface of the IR filter 14 or the light receiving region of the image sensor 12, because the housing 13 is rocked left and right when the focus adjustment is performed by rotating the lens barrel 14 mounted on the upper end portion of the housing 13. Therefore, when an image is reproduced by the image sensor 12, the particles have a large effect on the image.
Further, since the housing 13 and the lens barrel 14 are coupled though the male and female screws, the lens may be tilted along a spiral angle formed in the lens barrel 14 when the lens barrel 14 is rotated along the spiral contact surface.
Once foreign matters fall onto the lens 14c or the image sensor 12, they cannot be simply removed. Therefore, the camera module 10 in which the foreign matters have occurred should be discarded as a whole. As a result, the expensive lens 14c or the image sensor 12 is also discarded.
Further, since the housing 13 having the IR filter 15 coupled thereto is mounted on the printed board 11 after the image sensor 12 is wire-bonded to the printed board 11, movable foreign matters may fall into the housing 13, or specifically onto the upper end portion of the image sensor 12 such that defects frequently occur. Furthermore, since passive elements (not shown in FIG. 1) are mounted around the image sensor 12, flux or other foreign matters frequently occur.
Further, in order to quickly respond to users' request which changes day by day, a sample manufacturing schedule needs to be reduced by standardizing a camera module.